Depositional Textures Research Articles

Rock-physics diagnostics of depositional texture, diagenetic alterations, and reservoir heterogeneity in high-porosity siliciclastic sediments and rocks — A review of selected models and suggested work flows

Rock physics has evolved to become a key tool of reservoir geophysics and an integral part of quantitative seismic interpretation. Rock-physics models adapted to site-specific deposition and compaction help extrapolate rock properties away from existing wells and, by so doing, facilitate early exploration and appraisal. Many rock-physics models are available, each having benefits and limitations. During early exploration or in frontier areas, direct use of empirical site-specific models may not help because such models have been created for areas with possibly different geologic settings. At the same time, more advanced physics-based models can be too uncertain because of poor constraints on the input parameters without well or laboratory data to adjust these parameters. A hybrid modeling approach has been applied to siliciclastic unconsolidated to moderately consolidated sediments. Specifically in sandstones, a physical-contact theory (such as the Hertz-Mindlin model) combined with theoretical elastic bounds (such as the Hashin-Shtrikman bounds) mimics the elastic signatures of porosity reduction associated with depositional sorting and diagenesis, including mechanical and chemical compaction. For soft shales, the seismic properties are quantified as a function of pore shape and occurrence of cracklike porosity with low aspect ratios. A work flow for upscaling interbedded sands and shales using Backus averaging follows the hybrid modeling of individual homogenous sand and shale layers. Different models can be included in site-specific rock-physics templates and used for quantitative interpretation of lithology, porosity, and pore fluids from well-log and seismic data.

Microporous and tight limestones in the Urgonian Formation (late Hauterivian to early Aptian) of the French Jura Mountains: Focus on the factors controlling the formation of microporous facies

Microporous and tight limestones, with contrasting porosity and permeability values directly related to the microfabric of the micritic matrix, outcrop in the Urgonian Formation of the French Jura Mountains. This study investigates the factors controlling the differentiation between the microporous and tight facies, and proposes a diagenetic model for the development and preservation of the microporosity in these limestones. The petrophysical properties are not related to the depositional texture, the petrographical content or the mineralogical composition. However, the tight layers contain indications of emersion (e.g.: bird eyes, keystone vugs, and desiccation cracks). The sedimentation in very shallow conditions up to emersion is confirmed by the covariant more positive values of oxygen and carbon isotopes. The microporous intervals systematically occur a few meters below the tight layers affected by emersion. This position strongly suggests the importance of meteoric water input rapidly after sedimentation in the differentiation between tight and microporous limestones. The diagenetic model proposed for the development and preservation of the microporous facies involves partial early cementation of the interstitial mud, mainly composed of low-Mg calcite crystals (sedimentation during a calcite sea period), inside a meteoric phreatic lens by in situ dissolution–reprecipitation processes (“hybrid Ostwald ripening”). This early cementation partly preserves the original microfabric and intercrystalline microporosity and allows the carbonate sediment to resist compaction during burial. The identification of the conditions favorable to the development of microporosity in these Urgonian limestones may improve the knowledge and modeling of some microporous carbonate reservoir rocks.

Elastic moduli of dry and water-saturated carbonates — Effect of depositional texture, porosity, and permeability

Elastic moduli of water-saturated sedimentary rocks are in some cases different from moduli derived using Gassmann fluid substitution on data for rocks in the dry state. To address this discrepancy, we use a data set representing 115 carbonate samples from different depositional settings and a wide range of porosity and permeability. Depositional texture is reflected in the effect of water on elastic moduli and in the porosity-permeability relationship. Depositional texture is taken into account when porosity and permeability are combined in the effective specific surface of pores, which is related for a given pore fluid to the reference frequency as defined by Biot. For a given frequency of elastic waves, we obtain Biot’s frequency ratio between measured ultrasonic wave frequency and Biot reference frequency. For mostsamples with a frequency ratio above 10, elastic moduli in the water-saturated case are higher than predicted from elastic moduli in the dry case by Gassmann fluid substitution. This stiffening effect of water in some cases may be described by Biot’s high-frequency model, although in heterogeneous samples, a squirt mechanism is more probable. For data representing frequency ratios of 0.01 to 1, Gassmann fluid substitution works well. For samples with frequency ratios below 0.001, elastic moduli in the water-saturated case are lower than would be expected according to Gassmann’s equations or to Biot’s theory. This water-softening effect becomes stronger with decreasing frequency ratio. Water softening or stiffening of elastic moduli may be addressed by effective-medium modeling. In this study, we used the isoframe model to quantify water softening as a function of frequency ratio.

In Situ STM of 3-Mercaptopropanesulfonate Adsorbed on Pt(111) Electrode and Its Effect on the Electrodeposition of Copper

The adsorption of 3-mercaptopropanesulfonate (MPS) molecule on a Pt(111) single-crystal electrode and its effect on the deposition of Cu have been examined using in situ scanning tunneling microscopy (STM). MPS admolecules were irreversibly adsorbed in a largely disordered adlayer on bare Pt(111) in , irrespective of the presence of chloride, the concentration of MPS, and the applied potential. In comparison, the MPS admolecules readily formed a highly ordered molecular structure identified as on Pt(111) precoated with a monolayer of Cu adatoms. The MPS admolecules were adsorbed upright on Pt(111). The cyclic voltammetric results show that the MPS adlayer on Pt(111) would inhibit Cu deposition because the addition of MPS to the electrolyte of reduced the amount of the Cu deposit by half, even in the presence of chloride. The texture of the Cu deposit also varied with the surface state of the Pt(111) electrode as the Cu film grew in three-dimensional islands and smooth flakelike morphology on the MPS-modified and Cu-coated Pt(111) electrodes, respectively. In situ STM results indicated that the MPS admolecules stayed afloat rather than buried by the Cu deposit.

Characterization of pore system and their influence on decay rates caused by salt weathering on limestones and dolostones quarried in Abanto (Zaragoza, Spain)

The Abanto natural stone is a rock used in modern constructions and currently quarried as an ornamental rock in Abanto, Zaragoza. The varieties described here are a limestone with depositional texture and a crystalline limestone. In this work we have carried out a detailed study of the mineralogy, texture, hydric behaviour, pore system characteristics, dynamic behaviour and behaviour against the effects of salt crystallisation. After 30 cycles of salts crystallization, the weight loss in these rocks is lower than 0.5%. This low weathering is a consequence of the configuration of their pore system, characterised by a low open porosity and high percentages of microporosity with pore-throat sizes on average of less than a 0.2 µm. The petrographical and physical characteristics, as well as its high resistance against salt crystallisation confer these rocks a high technical quality for their use as building stones in modern construction.

Partitioning of sediment on the shelf offshore of the Columbia River littoral cell

Sediment derived from the Columbia River has been deposited on the continental shelf, along the barriers and beaches, and in the bays of the Oregon and Washington coast during the Holocene. The barrier and beach deposits of this 150-km section of coast comprise approximately 6 km 3 of these Holocene sediments (Peterson et al., 2010-this issue) while the fluvial and bay deposits comprise about 104 km 3 (Baker et al., 2010-this issue), and the shelf deposit is approximately 79 km 3. Seismic-reflection, sidescan sonar, and surface sediment data show that the shelf deposit is not uniform in distribution or composition. The shelf deposit is 15–50 m thick off the beaches of the southern part of the study area but is less than 3 m thick, and, in places, absent from the inner shelf in the northern third of the study area. Surface sediment texture of the shelf deposit varies as well. Pleistocene-age gravel covers parts of the inner shelf in the northern third of the area. To the south, the surface of the Holocene shelf deposit is composed of fine sand near shore that grades offshore to dominantly very fine sand in 25–30 m water depth and muddy sand on the middle and outer shelf (> 50 m depth). Although a huge volume of sediment covers the shelf, its uneven distribution indicates that in places only small amounts are available as a potential offshore source to the adjacent beaches, and in other places the finer-grained nature of the shelf deposit indicates that significant winnowing of fine sediment would be necessary to make it compositionally equivalent to sediment on adjacent beaches.

Characteristics of a sublacustrine fan in a half-graben rift lake basin and its petroleum prospects: Case study on the second member of the Tenggeer Formation, Saihantala Sag, Erlian Basin

Abstract Analysis has been carried out on the petrology, context and structure of sublacustrine fan sand bodies in the second member of the Tenggeer Formation. The sublacustrine fans are well developed, and are characterized by the Bouma sequence resulting from typical turbidite deposition and the presence of AAA and ABABAB sequences of non-typical turbidite systems. The depositional textures feature grain distributions typical of turbidite deposits and contain abundant turbidite deposit structures. The sublacustrine fans mainly develop in the lower part of the fault slope break formed by syn-sedimentary faulting in the fan delta front of the gentle slope in the sag and in the troughs in front of offshore subsea fan deposits in the down-thrown areas at boundary of the basin, controlled by an abrupt slope change. The formation of the sublacustrine fan is closely related to the long period of syn-sedimentary faulting activities, and the scale is controlled by the fault activity, slope gradient of palaeogeomorphology and the sediment supply. The sublacustrine fan sand bodies are adjacent to source rocks, and easily form lithologic traps and are favorable for petroleum migration and accumulation, which is significant for the petroleum prospecting in this area.

Surface Stratigraphy on Limestone of Venetian Palaces

The surfaces of Venetian palaces are a testimony to a long history of maintenance. Documents from nineteenth-century restoration projects assign dates and reveal some reasons for treatments explaining, for example, the use of aggressive cleaning and then the addition of pigments so that the newly restored façade did not appear ‘too white’. Restoration during the twenty-first century has presented the opportunity to study the stone surface of three palaces and their stratigraphy. Three types of layers were identified (pollution deposit, silica/wax treatment and corrosion) which overlay the original stone and show distinct elemental signatures. The texture of the outermost deposit showed that the particle size was greatest when it was derived from areas of greatest exposure to the wind compared with calmer sheltered parts. Waxy treatment layers contained strata that probably derived from the brush used to apply the treatment. These treatment layers were warmer in tone than the superficial deposit or underlying stone. Improved understanding of the stratigraphy can inform decisions as to what layers should be protected during restoration.

The southern fragment of the Siberian craton: "landscape" history over two billion years

The southern fragment of the Siberian craton: "landscape" history over two billion years

Environmental changes in the declining Middle Miocene Badenian evaporite basin of the Ukrainian Carpathian Foredeep (Kudryntsi section)

Environmental changes in the declining Middle Miocene Badenian evaporite basin of the Ukrainian Carpathian Foredeep (Kudryntsi section) The Kudryntsi section in West Ukraine documents a major environmental change from hypersaline to marine conditions during the Middle Miocene. There are very few (or no) specimens of foraminifers in samples of the siliciclastic series (4 m thick, with limestone intercalations) which occurs above the gypsum (and below the transgressive deposits) in the southern part of quarry. The limestone intercalations are first sparitic and microsparitic, and then become pelletal. The pelletal depositional textures are interpreted as originated in restricted environments in contrast to mixed-fossil lithoclastic packstones/grainstones overlying the siliciclastic series. The diversity of fauna increases up section. Foraminifers, bivalves, ostracods and gastropods appear first and then, additionally, brachiopods, bryozoans, crinoids, and echinoids occur. Foraminiferal assemblages are dominated by elphidiids forming 70 to 90 % of the population. The most common species are Elphidium crispum (Linné) and E. macellum (Fichtel & Moll). The limestones show a wide range of δ13C values (from -1.6 ‰ to - 18.2 ‰) and δ18O values (from -0.2 ‰ to -9.4 ‰) indicating that the cementation and some recrystallization took place in meteoric-water-dominated fluid but the restriction-controlled trend can be recognized. The siliciclastic series was deposited in an evaporitic lagoon influenced by large inflows of continental waters carrying the siliciclastic and other detrital material from the older Badenian rocks as well as from their substrate. The Kudryntsi section documents a stepwise decrease in water salinity — from ca. 150-300 ‰ during the Badenian gypsum precipitation, through ca. 80-150 ‰ during deposition of the siliciclastic series to ca. 35 ‰ during sedimentation of the basal transgressive deposits. The basal deposits originated in shallow subtidal (0-20 m) environments of normal marine salinity (30-35 ‰) and temperate to warm waters (8-18 °C) as indicated by requirements of the E. crispum association in recent seas.

Lithologic and diagenetic attributes of the Sharwayn (Maastrichtian) and Umm Er Radhuma (late Paleocene–Eocene) formations and their significance to the K-T unconformity, Jabal Samhan area, Dhofar, Sultanate of Oman

The boundary separating Maastrichtian Sharwayn Formation from late Paleocene Eocene Umm Er Radhuma (UER) Formation in Dhofar, southern Oman, is characterized by a regionally extensive unconformity. The Jabal Samhan escarpment, north of Marbat-Sadh transect, preserves this unconformable boundary. This paper addresses the lithologic and diagenetic differences of the strata across the boundary and discusses their significance and link to the development of the upper Maastrichtian to lower Paleocene unconformity. The upper part of the Sharwayn Formation is characterized by lower thickly bedded, bioclastic, and peloidal mudstone to wackestone lithofacies overlain by a thick ledge (~5.5 m) of medium to coarse crystalline, (sucrosic) dolostone. Poorly preserved outlines of the framework grains suggest an original peloidal and bioclastic grainstone texture for the dolostone unit. The contact with the overlying UER Formation is sharp. The UER Formation is characterized by thickly bedded, bioclastic mudstone to wackestone overlain by coarse-grained, foraminiferal grainstone. The dolomitization process of the dolomite unit at the top of the Sharwayn Formation is envisaged to a shallow subsurface mixed meteoric and sea water diagenetic realm. This interpretation is supported by an inferred timing of dolomitization of latest Maastrichtian (post-Sharwayn Formation) to early Paleocene (pre-EUR Formation), preservation (although poorly recognizable) of the original depositional texture and diagenetic features that postdate the sucrosic dolomite. Pervasive dolomitization of the dolomite unit was controlled by its original grainstone texture, which permitted efficient percolation of the dolomitizing fluids. Correlation between the reference section of the formation and the section studied in this work raises the thickness of the formation to 28.5 m (relative to a thickness of 22 m at the reference section). Analysis of the new composite section suggests that deposition of the formation took place in a shallowing-upward setting where low-energy subtidal sediments (the lower limestone unit) were succeeded by a high energy sand shoal (upper dolomitized unit).This shallowing-upward succession is attributed to a third-order sea-level drop. The later is also recognized in many parts of the Arabian Peninsula, as well as globally, and interpreted as eustatic sea-level fluctuation.

Controls on the Spatial Patterns of Carbon and Nitrogen in Adirondack Forest Soils along a Gradient of Nitrogen Deposition

We sampled 42 permanent vegetation plots in the Adirondack Mountains, NY to characterize the spatial patterns of, and controls on soil C and N contents. Average C (24 kg m−2) and N (1.1 kg m−2) contents of the combined organic and mineral horizons were high for northeastern U.S. forests. Contrary to our expectations, whole‐profile C and N amounts were not different among northern hardwood (NH), spruce‐fir (SF), and pine‐dominated (PW) plots. Most of the C and N were stored in organic horizons in the high‐elevation SF plots, and in the mineral horizons in NH and PW plots. Regression analyses of the pooled set of sites revealed that the factors that explained the most variability in soil C and N contents were different for organic and mineral horizons and differed between forest types. Overall, growing season degree‐days (GSDD) was the variable most closely correlated with C and N contents in both organic and mineral horizons, and varying combinations of N deposition, conifer importance, and soil texture were the principal secondary influences. Spruce‐fir plots received the most atmospheric N deposition, and multivariate regression tree (MRT) analysis indicated that N deposition rate was the environmental variable that explained the most variation in organic horizon C (sums of squares [SS] explained = 54%) and N (79% SS explained) amounts in these high‐elevation stands. However, even in the unlikely case of 100% retention of the atmospheric inputs of N deposited over the past 50 yr, this source only accounted for a small portion of soil N, and the differences in N among the plots along the deposition gradient. It is likely that differences in GSDD accounted for most of the differences in C and N amounts.

Microfacies and depositional environment of the Cenomanian of the Bangestan anticline, SW Iran

The Sarvak Formation (Albian to Turonian in age) of the Zagros basin is a thick sequence of shallow-water carbonates. This work focuses on the microfacies and sedimentary environment of the margin of the Cenomanian intrashelf basin. In the study area (southwest of Iran), the Sarvak Formation is subdivided into 12 microfacies that are distinguished by petrographic analysis on the basis of their depositional textures and fauna. In addition, four major depositional environments were identified in the Sarvak Formation. These include shelf lagoon, platform margin, slope and basin environmental settings, which are interpreted as a carbonate shelf without an effective barrier separating the platform from the open ocean.

Textured α-Alumina through Electrophoretic Deposition and Templated Grain Growth

The development of texture was studied during electrophoretic deposition in alumina suspensions containing plate shaped alumina particles. The mechanism of platelet orientation during EPD was examined with respect to the influence of the electric field, gravity and hydrodynamic forces. This was realized by using two different deposition cells, with vertically or horizontally positioned deposition electrode. The texture of the green deposit was further enhanced during sintering by templated grain growth in which the platelet shaped alumina particles were growing at the expense of the fine grained matrix. The sharp ‘fiber texture’ obtained after templated grain growth during sintering of the deposit was characterized by means of x-ray diffraction and Electron Backscatter Diffraction (EBSD).

Travertine deposits from along the South Tibetan Fault System near Nyalam, Tibet

AbstractA newly investigated travertine deposit in southern Tibet provides a window into Holocene hydrological, geomorphic and climatic processes near the boundary of the Tibetan Plateau and High Himalaya. Travertine, deposited as a result of the degassing of CO2-rich groundwater as it emerges on the Earth's surface, is in many cases formed along the trace of major crustal-scale faults in primarily extensional tectonic regimes. A travertine platform measuring roughly 1 km by 0.5 km exists near the town of Nyalam in southern Tibet along a major Himalayan down-to-the-N normal fault, the South Tibetan Fault System. A wide variety of travertine depositional textures and features are recorded in the platform on a series of terraces. Active travertine deposition was observed from spring mounds and seeps along the base of the platform at the modern river level. Palaeotemperatures of spring water, calculated from δ18O of the travertine, range from 9 to 25 °C, which closely matches the temperatures recorded from modern springs in the area. A complex geomorphological landscape records interaction between growing alluvial fans, travertine accumulation, and a rapidly down-cutting river with associated fluvial terraces. River incision was contemporaneous with travertine deposition, as indicated by cemented fluvial river gravel layers interbedded with travertine. High 87Sr/86Sr ratios in the travertine (mean of 0.7168) indicate subsurface fluid interaction with radiogenic crystalline rocks of the underlying Greater Himalaya. Uranium-series ages of the travertine platform range from 5400 a (±950 a) to 11600 a (±1000 a), and indicate a younging progression from higher terraces near the valley wall to lower terraces at present-day river level. Travertine that overlies a river gravel terrace 18 m above river level formed at 11600 a. This date yields a local incision rate of 1.6 mm a−1, consistent with estimated fluvial incision rates in the High Himalaya. The range of our U-series ages coincides with an interval of higher precipitation associated with greater intensity of the Indian monsoon, which led to elevated spring discharge and carbonate precipitation in this part of the High Himalayas.

Syneruptive features and sedimentary processes associated with pyroclastic currents entering the sea: the ad 79 eruption of Vesuvius, Bay of Naples, Italy

The ad 79 Plinian eruption of Vesuvius that buried Pompeii and Herculaneum began with pumice falls deposited towards the SE of the volcano followed by pyroclastic currents directed towards the SW. These currents reached Herculaneum and rapidly entered the sea, forming a fan. The interpretation of seismic reflection profiles and gravity cores collected off Herculaneum documents a submarine fan-shaped pyroclastic body at 10–140 m water depth that we interpret as the submarine counterpart of the onshore pyroclastic current deposits. This fan, c . 0.3 km 3 in volume, displays a chaotic seismic facies that changes seaward to parallel reflectors and then to wavy reflectors. Gravity cores reveal a succession consisting of centimetre-thick sand- or silt-sized ash couplets followed by a graded gravelly sand-sized bed up to 180 cm thick, containing shell fragments and beach-derived pebbles, overlain by centimetre-thick graded and laminated sandy ash layers. The depositional textures and sedimentary structures of the submarine pyroclastic fan have been interpreted as the product of the interactions between pyroclasts, water waves and tsunamis induced by the ad 79 pyroclastic density currents into the Bay of Naples.

Development, composition and age of indurated sand layers in the Late Quaternary coastal deposits of northern Moreton Bay, Queensland

Indurated sand in the Late Quaternary coastal plain succession of northern Moreton Bay was examined in sand-mine pits, drillcores and the eroded bank of an estuarine channel. Samples show that the cements usually coat grains and partially infill interstitial pores. Distinctive cement habits reflect different constituents that are dominantly kaolinite and amorphous organic-rich complexes. Trace-metal concentrations in the cements are lower than previously reported for soils and estuarine sediments in the study region. Optically stimulated luminescence and thermoluminescence ages of these deposits indicate that pedogenic induration occurs over long periods, up to approximately 90 000 years, with only incipient induration evident in deposits 16 000 – 2600 years old. However, the rate of induration is far higher in relatively coarse channel fill, in which mineral and amorphous organic-rich cements have precipitated from shallow groundwater that flowed laterally through the deposit. The degree of induration, therefore, is strongly influenced by the original depositional texture and morphology of deposits, with well-indurated gravely channel fill (76 700 ± 6500 y), at least 2 m thick, sitting adjacent to medium-grained sand probably of dune origin, which contains a 30 cm-thick induration horizon (98 000 ± 9900 y).

Some major problems with existing models and terminology associated with kimberlite pipes from a volcanological perspective, and some suggestions

Five significant problems hinder advances in understanding of the volcanology of kimberlites: (1) kimberlite geology is very model driven; (2) a highly genetic terminology drives deposit or facies interpretation; (3) the effects of alteration on preserved depositional textures have been grossly underestimated; (4) the level of understanding of the physical process significance of preserved textures is limited; and, (5) some inferred processes and deposits are not based on actual, modern volcanological processes. These issues need to be addressed in order to advance understanding of kimberlite volcanological pipe forming processes and deposits. The traditional, steep-sided southern African pipe model (Class I) consists of a steep tapering pipe with a deep root zone, a middle diatreme zone and an upper crater zone (if preserved). Each zone is thought to be dominated by distinctive facies, respectively: hypabyssal kimberlite (HK, descriptively called here massive coherent porphyritic kimberlite), tuffisitic kimberlite breccia (TKB, descriptively here called massive, poorly sorted lapilli tuff) and crater zone facies, which include variably bedded pyroclastic kimberlite and resedimented and reworked volcaniclastic kimberlite (RVK). Porphyritic coherent kimberlite may, however, also be emplaced at different levels in the pipe, as later stage intrusions, as well as dykes in the surrounding country rock. The relationship between HK and TKB is not always clear. Sub-terranean fluidisation as an emplacement process is a largely unsubstantiated hypothesis; modern in-vent volcanological processes should initially be considered to explain observed deposits. Crater zone volcaniclastic deposits can occur within the diatreme zone of some pipes, indicating that the pipe was largely empty at the end of the eruption, and subsequently began to fill-in largely through resedimentation and sourcing of pyroclastic deposits from nearby vents. Classes II and III Canadian kimberlite models have a more factual, descriptive basis, but are still inadequately documented given the recency of their discovery. The diversity amongst kimberlite bodies suggests that a three-model classification is an over-simplification. Every kimberlite is altered to varying degrees, which is an intrinsic consequence of the ultrabasic composition of kimberlite and the in-vent context; few preserve original textures. The effects of syn- to post-emplacement alteration on original textures have not been adequately considered to date, and should be back-stripped to identify original textural elements and configurations. Applying sedimentological textural configurations as a guide to emplacement processes would be useful. The traditional terminology has many connotations about spatial position in pipe and of process. Perhaps the traditional terminology can be retained in the industrial situation as a general lithofacies-mining terminological scheme because it is so entrenched. However, for research purposes a more descriptive lithofacies terminology should be adopted to facilitate detailed understanding of deposit characteristics, important variations in these, and the process origins. For example every deposit of TKB is different in componentry, texture, or depositional structure. However, because so many deposits in many different pipes are called TKB, there is an implication that they are all similar and that similar processes were involved, which is far from clear.

A new approach to kimberlite facies terminology using a revised general approach to the nomenclature of all volcanic rocks and deposits: Descriptive to genetic

Although kimberlite pipes/bodies are usually the remains of volcanic vents, in-vent deposits, and subvolcanic intrusions, the terminology used for kimberlite rocks has largely developed independently of that used in mainstream volcanology. Existing kimberlite terminology is not descriptive and includes terms that are rarely used, used differently, and even not used at all in mainstream volcanology. In addition, kimberlite bodies are altered to varying degrees, making application of genetic terminology difficult because original components and depositional textures are commonly masked by alteration. This paper recommends an approach to the terminology for kimberlite rocks that is consistent with usage for other volcanic successions. In modern terrains the eruption and emplacement origins of deposits can often be readily deduced, but this is often not the case for old, variably altered and deformed rock successions. A staged approach is required whereby descriptive terminology is developed first, followed by application of genetic terminology once all features, including the effects of alteration on original texture and depositional features, together with contact relationships and setting, have been evaluated. Because many volcanic successions consist of both primary volcanic deposits as well as volcanic sediments, terminology must account for both possibilities.

Aligned-Crystalline Si Films on Non-Single-Crystalline Substrates

AbstractWe summarize recent progress in growth and characterization of aligned-crystalline silicon (ACSi) films on polycrystalline metal and amorphous glass substrates. The ACSi deposition process uses, as a key technique, ion-beam-assisted deposition (IBAD) texturing on a non-single-crystalline substrate to achieve a biaxially-oriented (i.e., with preferred out-of-plane and in-plane crystallographic orientations) IBAD seed layer, upon which homo- and hetero-epitaxial buffer layers and hetero-epitaxial silicon (i.e., ACSi) films with good electronic properties can be grown. We have demonstrated the versatility of our approach by preparing ACSi films on customized architectures, including fully insulating and transparent IBAD layer and buffer layers based on oxides on glass and flexible metal tape, and conducting and reflective IBAD layer and buffer layers based on nitrides on flexible metal tape. Optimized 0.4-μm-thick ACSi films demonstrate out-of-plane and in-plane mosaic spreads of 0.8° and 1.3°, respectively, and a room-temperature Hall mobility of ∼90 cm2/V.s (∼50% of what is achievable with epitaxial single-crystalline Si films, and ∼1000 times that of amorphous Si films) for a p-type doping concentration of ∼4×1016 cm−3. By using various experimental techniques, we have confirmed the underlying crystalline order and the superior electrical characteristics of low-angle (<5°) grain boundaries in ACSi films. Forming gas anneal experiments indicate that Si films with low-angle grain boundaries do not need to be passivated to demonstrate improved majority carrier transport properties. Measurements on metal-insulator-semiconductor structures using ACSi films yield near-electronic-grade surface properties and low surface defect densities in the ACSi films. A prototype n+/p/p+–type diode fabricated using a 4.2-μm-thick ACSi film shows minority carrier lifetime of ∼3 μs, an estimated diffusion length of ∼30 μm in the p-Si layer with a doping concentration of 5×1016 cm−3, and external quantum efficiency of ∼80% at 450 nm with the addition of an MgO film anti-reflector.